US3461344A

US3461344A - Solid state matrix for display system or the like

Info

Publication number: US3461344A
Application number: US706100A
Authority: US
Inventors: Leonard G Rich
Original assignee: Gerber Scientific Instrument Co
Current assignee: Gerber Systems Corp
Priority date: 1968-02-16
Filing date: 1968-02-16
Publication date: 1969-08-12
Anticipated expiration: 1986-08-12
Also published as: DE1814003A1; GB1232405A; JPS494800B1; DE1814003C3; DE1814003B2

Description

Aug, 12, 1969 L. G. RICH 3,461,344

SOLID STATE MATRIX FOR DISPLAY SYSTEM OR THE LIKE Filed Feb. 16. 1968 2 Sheets-Sheet 1 CONDUCTOR RESISTIVE DOTS uenr sm'r'rms 001s TRANSPARENT CONDUCTOR TRIGGERING LOGIC FIG. 3

INVENTOR. LEONARD G. RICH ATTORNEYS 69 L. G. RICH 4 3,461,344

SOLID STATE MATRIX FOR DISPLAY SYSTEM OR THE LIKE Filed Feb. 16, 1968 2 Sheets-Sheet 2 i 44" //v 4 4 4 I /7 FlG.6/

FIG. 8

United States Patent 3,461,344 SOLID STATE MATRIX FOR DISPLAY SYSTEM OR THE LIKE Leonard G. Rich, West Hartford, Conn., assignor to The Gerber Scientific Instrument Company, South Windsor, Conn., a corporation of Connecticut Filed Feb. 16, 1968, Ser. No. 706,100 Int. Cl. H!) 37/02, 39/08 U.S. Cl. 315-469 16 Claims ABSTRACT OF THE DISCLOSURE A solid state device consists of a matrix of four layer semiconductor switch elements which may be individually and selectively triggered between conducting and nonconducting states and which remain in their last triggered state until retriggered or otherwise deliberately returned to the opposite state. The current passing through the switch elements is used to excite light-emitting elements electrically connected with the switch elements and distributed in a regular pattern over one face of the matrix. Therefore, by properly individually triggering given switch elements to a conducting state a radiant output is produced which may be used as a visible display or as a means for producing photographically drawings or other graphic permanent records. As an alternative to a radiant output, the current passing through the switch elements may be used to activate an electro-sensitive paper or the like to produce a drawing or other graphic record on the paper. Also, as a further alternative, the device may be designed to operate in a flash manner wherein each stack, when triggered to a conducting state, thereafter quickly reverts to its non-conducting state so that the output element activated by the current through the switch element is excited for only a short predetermined interval of time.

Background of invention This invention relates to display systems or the like wherein a visible display or drawing is made by selectively exciting discrete minute portions of a display or output surface, and it deals more particularly with the construction of a solid state matrix device which provides such an output surface, the matrix being divided into a large number of individual units each exclusively associated with a particular minute portion of the surface and connected so as to be readily selectively addressable by triggering or other control signals.

Summary of invention The solid state matrix device of this invention includes a display or output surface divided into a very large number of minute discrete portions or dots arranged in a regular pattern over the surface. Each of these dots may be a small light-emitting element which, when excited by an electric current, emits radiant light energy, or may merely constitute an electrode for passing an electric current through an electro-sensitive paper or the like placed against the output surface. Associated with each discrete portion or dot of the display surface is a semiconductor switch element which functions generally similarly to a silicon controlled rectifier and which may be triggered between conducting and non-conducting states to. permit or prevent electric current from a suitable source to pass through the switch element to the associated dot of the output surface. The device may be made by well-known integrated circuit techniques and preferably constitutes a number of layers of different material superimposed on one another with the material of each layer divided into separate dots or other shapes and properly arranged and ice registered with the material of the other layers as to form individual stack-like units arranged in a regular pattern of rows and columns. The basic part of each stack-like unit of the matrix device is the switch element which is comprised of four alternately doped layers of semiconductive material. The second layer of all of the switch elements associated with one row of stack-like units are electrically connected in common. Similarly, the third layers of all of the switch elements in each column of stack-like units are connected in common, with the result that any one particular switch element may be triggered to a conducting state by simultaneously applying triggering signals to the column and row terminals which intersect at said switch element. Therefore, by combining the matrix device of this invention with a computer or other logic device which provides a system of sequencing the control of the triggering signal drive on the columns and rows is possible to produce a continuously variable controllable display system.

Brief description of the drawing FIG. 1 is an enlarged, exploded, and somewhat schematic view of a solid state matrix device embodying this invention.

FIG. 2 is an enlarged, somewhat schematic view of the solid state matrix device of FIG. 1 as incorporated in a display system.

FIG. 3 is a schematic diagram illustrating the equivalent electrical circuit for two of the stack-like units in the matrix device of FIG. 1.

FIG. 4 is a still greater enlarged view showing schematically the different layers making up one of the stack-like units of the matrix device of FIG. 1.

FIG. 5 is a view generally similar to FIG. 4 but shows a one stack-like unit of a matrix device comprising an alternate embodiment of the invention.

FIG. 6 is a view generally similar to FIG. 4 but shows one stack-like unit of a matrix device comprising still another embodiment of the invention.

FIG. 7 is a view generally similar to FIG. 4 but shows two stack-like units of a matrix device comprising still another embodiment of the invention.

FIG. 8 is a view taken on the line 88 of FIG. 7.

Description of the preferred embodiments Turning now to the drawings, FIGS. 1 and 2 show in greatly enlarged form a solid state matrix device 10 embodying this invention. The illustrated device 10 may be taken as substantially complete, but normally an actual device would consist of a very much larger number of stack-like units. Also, in FIGS. 1 and 2 various terminals required for making electrical connection with various parts of the device 10 have been eliminated for clarity. Such terminals may be added to the device in any well known manner and by themselves form no essential part of the invention. As is obvious from FIGS. 1 and 2 the device 10 is formed of a number of different layers of material superimposed on one another, and in FIG. 1 the device is shown in an exploded form with the various different layers separated from one another.

Considering FIGS. 1 and 2 in more detail, the device 10 there shown includes four layers 12, 13, 14 and 15 of semiconductor material which together'form the basic switch elements of the various stack-like units. The bottom layer 12 consists of a large number of small discrete areas or

deposits

16, 16 of semiconductive material. In the illustrated case the

areas

16, 16 are shown to be generally square in shape, and for convenience these small areas or deposits of material, and similar areas or deposits of material in other parts of the device, will be referred to hereinafter as dots. These dots, however,

. 3 need not be square in shape andmay be circular or any other suitable shape, the term dot being intended to apply to any such shape. In the layer 12, the

dots

16, 16 are arranged in a regular pattern to form five rows of dots extending generally parallel to the arrow 17 and six columns of dots extending generally parallel to the arrow 18. In the areas not covered by the

dots

16, 16 the layer 12 includes a suitable electrical insulating material 20 which electrically isolates the dots from one another.

The layer 13 immediately above the bottom layer 12 consists of a number of

strips

22, 22 of semicond'uctive material which extend generally parallel to the rows of

dots

16, 16 in the bottom layer 12 and each of which directly overlies a respective one of said rows. The layer 14 immediately above the layer 13 consists of a number of

strips

24, 24 of semiconductive material, each extending along and located directly above a respectiveone of the columns of the

dots

16, 16 of the layer 12. The top layer 15 consists of a number of

dots

26, 26 of semiconductive material arranged in the same pattern as the

dots

16, 16 of the layer 12 and each located directly above a respective one of the

dots

16, 16. The spaces between the

strips

22, 22 of the layer 13, the

strips

24, 24 of the layer 14 and the

dots

26, 26 of the layer 15 are filled with the electrical insulating material 20.

-The four semiconductive layers 12, 13, 14 and 15 may be formed in accordance with various different well known methods for forming multi-layered integrated circuit devices, as for example by forming each layer epitaxially through the use of suitable masks. The semiconductive materials used in the four layers are alternately doped with approximately the same concentrations of impurities as used in the corresponding layers of a silicon controlled rectifier. As shown in FIG. 1 the dots 2 6, 26 of the layer 15 are of -p-type conductivity material, the

strips

24, 24 of the layer 14 are of n-type conductivity material, the

strips

22, 22 of the layer 13 of p-type conductivity material and the

dots

16, 16 of the layer 12 are of n-type conductivity material. It will therefore be evident that in the device 10, a large number of PNPN semi-conductor switch elements are provided with each being comprised of one dot 16 of the bottom layer 12, one strip 22 of the next layer 13, one strip 24 of the layer 14 and one dot 26 of the top layer 15. It should be understood, however, that although a PNPN configuration has been shown for these switch elements they could as well be made of an NPNP configuration without departing from the invention.

In addition to the four semiconductive layers 12,13, 14 and 15 which form the basic switch units, the device 10 of FIGS. 1 and 2 further includes a light-emitting layer 28 made up of a large number of elements or dots 30, 30 arranged in the same pattern as the

dots

16, 16 of the layer 12 and each registered with a respective one of the (

lots

16, 16. Each dot 30 is of such a nature as to emit light radiation when excited by an electric currentpassing therethrough from the associated dot 16. Various different materials may be used to form the dots 30, 30, but preferably each dot 30 is a small light-emitting diode, and when this is the case each element 30 may 'either be a two layer diode by itself or may be a single layer of material with the material of the associated dot 16 forming the other part of the diode. Insulating material 20 fills spaces between the individual dots 30, 30 to electrically isolate them from one another.

.Below the light-emitting layer 28 is a layer 32 of transparent conductive material which allows the radiation emitted by the light emitting dots 30, 30 to pass therethrough and which serves as a common terminal elec- -the light emitted by the dots 30, 30 is in the visible range. This picture or graphic display may be viewed directly by a user or may be used to expose a photosensitive sheet placed over the bottom surface to photographically produce a permanent record of the display.

As a means for supplying exciting current to each of the switch elements of the device 10, the device further includes two additional layers above the top semiconductive layer "15. The layer 36 immediately above the layer 15 is referred to as an ohmic layer and consists of a large number of dots 38, 38 of ohmic material, which dots 38, 38 are arranged in the same pattern as the

dots

26, 26 of the layer 15 with each registered with a re spective one of the latter d'ots. Above the layer 36 is a final layer 40 consisting of a sheet of conductive .material which electrically connects all of the top surfaces of the ohmic or resistive dots 38, 38. If desired, the ohmic dots 38, 38 may be formed by forming a coating of ohmic material on the conductive sheet forming the layer 40, prior to its assembly with the remainder of the device 10, and by then scribing the ohmic layer to divide it into the dots 38, 38.

FIG. 4 shows a vertical section taken through one stack-like unit 42 of the device of FIG. 1, and FIG. 3 shows a general electrical equivalent or transistor analog of two

adjacent units

42, 42. In FIG. 3 the various parts of the equivalent circuit have been given the same reference numbers as the elements of the device 10 to which they are generally equivalent. From these figures it will therefore be evident that in each unit the two

dots

16 and 26 and two

strips

22 and 24 of semiconductive material form a triggered switch, generally similar to a silicon controlled rectifier. Also, from FIG. 3 it will be evident that by proper biasing each such triggered switch may be made to operate in such a fashion that a negative triggering signal must be applied to strip 24 simultaneously with a positive triggering signal applied to the strip 22 in order to switch it from a non-conducting to a conducting state, and that once it is rendered conducting it will remain in such conducting state until turned off by a further turn off procedure as, for example, simultaneously applying reverse triggering pulses to the strip 24 and the strip 22 or momentarily turning off all points to momentarily reduce all currents through the device 10 to zero.

As shown in FIGS. 2 and 4, the upper and lower

conductive layers

32 and 40 of the device 10 are connected to a suitable voltage source 44 so that when a particular element 42 is switched to a conducting state current flows therethrough from the source 44 to excite the associated light-emitting element 30. The ohmic element 38 of each stack-like unit 42 serves as a current limiting device and in some cases may be eliminated. FIG. 2 shows a typical application of the device 10 wherein all of the

strips

24, 24 of the layer 14 and all of the

strips

22, 22 of the layer 13 are connected to a triggering logic 46 which may, for example, be part of a computer. Because of the

strips

22, 22 extending in one direction and the

strips

24, 24 extending in another direction, each stack-like unit in the device 10 is selectively addressable by triggering signals applied simultaneously to the strip 22 and the strip 24 which intersect and are exclusively paired in that particular unit. Therefore, the triggering logic 46 by properly sequencing triggering signals to the

strips

24, 24 and 22, 22 may be used to excite those light-emitting elements required to produce a desired display on the output surface 34 of the device 10. Of course, as mentioned previously, the number of stack-like units in the device 10 may be increased very greatly beyond the number shown in FIGS. 1 and 2 to produce a relatively large output surface divided into very small discrete dots. It should also be understood that by proper selection of the material used for providing the light-emitting dots, the device 10 is capable of producing color. The device 10 could therefore be designed for use in a system capable of providing both monocrome and color displays and pictures. Also, the triggering logic 46, could be such as to rapidly and repeatedly change the picture or display produced at the output surface 34 to produce a moving picture as in television, the device thereby becoming the equivalent of a fiat television tube.

FIG. 5 is a section taken through one stack-like unit of a matrix device, indicated generally at 48, which is generally similar to the device 10 of FIGS. 1 to 4, except for omission of the light-emitting layer 28and the transparent conductive layer 32 of the device 10. Parts of the device 48 which are similar to corresponding parts of device 10 have been given corresponding reference numbers and need not be further redescribed. In the device 48, the output surface 50 is located at the bottom of the semiconductive layer 12 with the lower face of each semiconductive dot 16 forming a small part of said output surface. In use the device 48 has its upper conductive surface connected to the positive side of a suitable voltage source 52, and the negative side of the source 52 is connected to a conductive bed or plate 54. An electrosensitive paper 56 or the like is placed between the output surface 50 and the upper surface of the bed 46 so that each dot 16 of the device 48 contacts a small discrete area of the paper 56. Therefore, when the switch element of which the illustrated dot 16 is a part is triggered to its conducting state current flows through the electro-sensitive paper 56, from the dot 16 to the bed 54, and electrically activates the paper over the area covered by the dot. Therefore, if the paper 16 is one which changes color or tone as a result of electrical activation, a picture or other graphic display may be made on it by properly triggering selected ones of the switch elements making up the device 48.

As an alternative to a matrix device wherein the individual switch elements remain in a conducting state until deliverately turned to a non-conducting state, a matrix device embodying this invention may also be made for use in a flash mode of operation wherein each switch element once triggered to its conducting state remains in such conducting state for a predetermined length of time and is then automatically returned to its non-conducting state. To achieve this kind of operation the matrix device is constructed so as to include a plurality of capacitors each associated with a respective one of the switch elements.

FIG. 6 shows a matrix device 58 incorporating one form of capacitor. Parts of the device 58 which are similar to corresponding parts of the device 10 of FIGS. 1 to 4 have been given the same reference numbers as in FIGS. 1 and 4 and need not be re-described. The device 58 is identical to that of the device 10 except for including in each stacklike unit a dot of material 60 replacing the ohmic dot 38 of FIG. 1. The material of the dot 60 is one, such as barium titanate, having a high dielectric constant and a slight electrical conductivity so as to form a leaky capacitor between the semiconductive dot 26 and the conductive layer 40. In the use of the device 58, when simultaneous triggering signals are applied to the strip 22 and the strip 24 of a particular switch element, the switch element conducts to excite its associated light-emitting dot 30 and to charge the capacitor formed by the associated dielectric dot 60. As this capacitor becomes charged the current through the switch element device falls below the conduction sustaining level and the switch thereupon reverts to its non-conducting state, the capacitor thereupon discharging through the material of the dot 60 to make itself ready for another cycle of operation.

FIGS. 7 and 8 show a section through two adjacent stack-like units of a matrix device 62 in which a capacitor for each unit is formed by replacing the ohmic layer 36 of the device 10 of FIGS. 1 to 4 with a conductive layer 64 and a dielectric layer 66. The conductive layer, as best shown in FIG. 8, includes a number of

dots

68, 68 of conductive material arranged in the same pattern as the

dots

26, 26 of the layer and registered with the

dots

26, 26. Surrounding each of the conductive dots 68 is a region of ohmic material 70, and in the otherwise empty space beyond the outer edge of the regions 70, is a common conductive material 72. As a result, each conductive dot 68 is connected to the common conductor 72 through a resistance provided by the associated ohmic material 70. The dielectric layer 66, in turn, includes a number of dots of dielectric material 74, 74 arranged in the same pattern as the dots of

conductive material

68, 68 and registering with the latter dots, the spaces between the dots 74, 74 being filled with electric insulating material 20 so as to electrically isolate the dielectric dots 74, 74 from one another.

In the use of the device 62 of FIGS. 7 and 8, the common conductor 72 of the conductive layer 64 is connected to one side of a suitable voltage source 76 and the other side of the source is connected to the transparent conductive layer 32. The transparent conductive layer 32 is also grounded as is the upper conductive layer 40. Therefore, when a particular stack-like unit of the device 62 is in its non-conducting state the associated capacitor, formed by the dielectric dot 74, the conductive dot 68 and conductive layer 62, is charged. When simultaneous triggering signals are applied to the

strips

22 and 24 of this particular stack-like unit, the unit is rendered conductive and conducts through it the charge of its associated cacapitor, this conduction being maintained until the capacitor becomes discharged to the point where the current falls below the conduction sustaining level. Thereafter, the device reverts to its non-conducting state and the capacitor recharges for a new operating cycle.

The drawings show preferred embodiments of the invention and such embodiments have been described above, but it will be understood that various changes may be made from the constructions disclosed, and that the drawings and description are not to be construed as defining or limiting the scope of the invention, the following claims forming a part of this specification being relied upon for that purpose.

I claim:

1. A solid state matrix device comprised, at least in part, of four layers of semiconductive material superimposed on one another and forming a plurality of switch elements which may be selectively triggered between conducting and non-conducting states, the bottom one of said layers consisting of a plurality of individual dots of semiconductive material of one type conductivity arranged regularly in a number of columns extending in one direction and a number of rows extending in another direction, the layer immediately above said bottom layer consisting of a plurality of individual strips of semiconductive material of opposite type conductivity arranged so as to extend along and overlie said rows of said dots in said bottom layer, the layer immediately above said layer of row-wise oriented strips consisting of a plurality of individual strips of semiconductive material of said one type conductivity which latter strips are arranged so as to extend along and overlie said columns of said dots in said bottom layer, and the top one of said layers consisting of a plurality of individual dots of semiconductive material of said opposite type conductivity arranged in the same pattern as the dots of said bottom layer so that each overlies a respective one of said latter dots.

2. A solid state matrix device as defined in claim 1 further characterized by a layer of ohmic material immediately above said top layer of said four layers of semiconductive material, said ohmic layer consisting of a plurality of individual dots of ohmic material arranged in the same pattern as the dots of said top layer so that each overlies a respective one of said latter dots.

3. A solid state matrix device as defined in claim 2 further characterized by a layer of conductive material located immediately above said ohmic layer and electrically connecting the top surfaces of all of said dots of ohmic material.

4. A solid state matrix device as defined in claim 1 further characterized by a light-emitting layer of material located immediately below said bottom layer of said four layers of semiconductive material, said lightemitting layer consisting of a plurality of individual elements arranged in the same pattern as said dots of said bottom layer so that each overlies a respective one of said latter dots, each of said elements of said lightemitting layer being of such nature as to emit light radiation when an electric current passes between it and said respectively associated one of said dots of said bottom layer.

5. A solid state matrix device as defined in claim 4 further characterized by each of said elements of said light-emitting layer comprising a quantity of semiconductive material forming a light-emitting diode in conjunction with said respectively associated dot of said bottom layer.

6. A solid state matrix device as defined in claim 4 further characterized by a layer of transparent conductive material located below said light-emitting layer.

7. A solid state matrix device as defined in claim 1 further characterized by means forming a plurality of capacitors above said top layer of said four layers of semiconductive material with each of said capacitors having one terminal electrically connected with a respective one of said dots of said top layer and having its other terminal connected in common to the corresponding terminals of the other of said capacitors.

8. A solid state matrix device as defined in claim 7 further characterized by said means forming a plurality of capacitors comprising a dielectric layer located immediately above said top layer of said four layers of semiconductive material and consisting of a plurality of dots of material of high dielectric constant arranged in a pattern similar to that of said dots of said top layer so each overlies a respective one of said latter dots, and a layer of conductive material above said dielectric layer electrically connecting the top surfaces of all of said dots of dielectric material.

9. A solid state matrix device as defined in claim 7 further characterized by said means forming a plurality of capacitors comprising a first terminal layer immediately overlying said top layer of said four layers of semiconductive material, a dielectric layer overlying said first terminal layer, said first terminal layer comprising a plurality of conductive dots arranged in the same pattern as said dots of said top layer of said four layers of semiconductive material and arranged so that each engages the top surface of a respective one of said latter dots, said first terminal layer further including a common conductor spaced from each of said conductive dots and an ohmic material between each of said conductive dots and said common conductor, said dielectric layer comprising a plurality of dots of material of high dielectric constant arranged in a pattern similar to that of said conductive dots and arranged so that each overlies a respective one of said latter dots, and a layer of conductive material above said dielectric layer electrically connecting the top surfaces of all of said dots of dielectric material.

10. A solid state matrix device as defined in claim 1 further characterized by a layer of ohmic material immediately above said top layer of said four layers of semiconductive material, said ohmic layer consisting of a plurality of individual dots of ohmic material arranged in the same pattern as said dots of said top layer so that each overlies a respective one of said latter dot-s, a layer of conductive material located immediately above said ohmic layer so as to electrically connect the top surfaces of all of said dots of ohmic material, a light-emitting layer of material located immediately below said bottom layer of said four layers of semiconductive material, said light-emitting layer consisting of a plurality of individual elements arranged in the same pattern as said dots of said bottom layer so that each underlies a respective one of said latter dots, each of said elements of said light emitting layer being of such nature as to emit light radiation when an electric current passes between it and said respectively associated one of said dots of said bottom layer and a layer of transparent conductive material located below said light-emitting layer.

11. A solid state matrix device having an output surface divided into a large number of discrete dots arranged regularly in a number of columns extending in one direction and a number of rows extending in another direction, said matrix device including a plurality of semiconductor switch devices each exclusively electrically connected with a respective one of said dots and each consisting of four alternately doped layers of semiconductive material, the second and third of said four layers being located between the first and fourth of said four layers, means electrically connecting in common the second layers of said switch devices associated with each of said rows of dots, and means electrically connecting in common the third layers of said switch devices associated with each of said columns of dots.

12. A solid state matrix device as defined in claim 11 further characterized by each of said dots being defined by one surface of a light-emitting element electrically connected with a respective one of said semiconductor switch devices and of such nature as to emit light radiation when an electric current passes'through it from said associated semiconductor switch device.

13. A solid state matrix device as defined in claim 11 further characterized by each of said dots being defined by one surface of said first and second layers of its associated semiconductor switch device.

14. A solid state matrix device having an output surface divided into a large number of discrete dots arranged regularly in a number of columns extending in one direction and a number of rows extending in another direction, said matrix device including a plurality of semiconductor switch devices each exclusively electrically connected with a respective one of said dots and each including first and second layers of semiconductive material to which simultaneous triggering signals need be applied to switch it from a non-conducting to a conducting state, means electrically connecting in common the said first layers of said switch devices associated with each of said rows of dots, and means electrically connecting in common the said second layers of said switch devices associated with each of said columns of dots.

15. A solid state matrix device as defined in claim 14 further characterized by each of said dots being defined by one surface of a light-emitting element electrically connected with a respective one of said semiconductor switch devices and of such nature as to emit light radiation when an electric current passes through it from said associated semiconductor switch device.

16. A solid state matrix device as defined in claim 14 further characterized by each of said dots being defined 'by one surface of said first and second layers of its associated semiconductor switch device.

-' References Cited UNITED STATES PATENTS 3,214,595 10/1965 Johnson et al 2502l9 3,258,644 6/1966 Rajchman 31555 3,375,373 3/1968 Hageman 250-209 3,388,255 6/1968 May 250-209 JOHN W. HUCKERT, Primary Examiner S. BRODER, Assistant Examiner U.S. Cl. X.R.